Rag doll in game engine?
Create two rigid body armatures, one with animations, and one without animations. Constrain the bones of the rag doll to the rigid objects. switch between the both of them at the moment you want to let it fall. You should probably create a python script where you copy the location and orientation of the animated armature to the rigid objects. After that you just set the animated armature to invisible, and the other to visible.